Add real-time log monitoring and system stats dashboard

Implements a comprehensive monitoring system for the admin interface:

Backend:
- New monitoring package with Redis ring buffer for log storage
- Zerolog MultiWriter to capture logs to Redis
- System stats collection (CPU, memory, disk, goroutines, GC)
- HTTP metrics middleware (request counts, latency, error rates)
- Asynq queue stats for worker process
- WebSocket endpoint for real-time log streaming
- Admin auth middleware now accepts token in query params (for WebSocket)

Frontend:
- New monitoring page with tabs (Overview, Logs, API Stats, Worker Stats)
- Real-time log viewer with level filtering and search
- System stats cards showing CPU, memory, goroutines, uptime
- HTTP endpoint statistics table
- Asynq queue depth visualization
- Enable/disable monitoring toggle in settings

Memory safeguards:
- Max 200 unique endpoints tracked
- Hourly stats reset to prevent unbounded growth
- Max 1000 log entries in ring buffer
- Max 1000 latency samples for P95 calculation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

pkg/utils/logger.go

@@ -12,22 +12,48 @@ import (
 
 // InitLogger initializes the zerolog logger
 func InitLogger(debug bool) {
+	InitLoggerWithWriter(debug, nil)
+}
+
+// InitLoggerWithWriter initializes the zerolog logger with an optional additional writer
+// The additional writer receives JSON formatted logs (useful for monitoring)
+func InitLoggerWithWriter(debug bool, additionalWriter io.Writer) {
 	zerolog.TimeFieldFormat = time.RFC3339
 
-	var output io.Writer = os.Stdout
-
 	if debug {
-		// Pretty console output for development
-		output = zerolog.ConsoleWriter{
-			Out:        os.Stdout,
-			TimeFormat: "15:04:05",
-		}
 		zerolog.SetGlobalLevel(zerolog.DebugLevel)
 	} else {
-		// JSON output for production
 		zerolog.SetGlobalLevel(zerolog.InfoLevel)
 	}
 
+	// Build the output writer(s)
+	var output io.Writer
+
+	if additionalWriter != nil {
+		// Always write JSON to additional writer for monitoring
+		// The additional writer parses JSON to extract log entries
+		if debug {
+			// In debug mode: pretty console to stdout + JSON to additional writer
+			consoleOutput := zerolog.ConsoleWriter{
+				Out:        os.Stdout,
+				TimeFormat: "15:04:05",
+			}
+			output = io.MultiWriter(consoleOutput, additionalWriter)
+		} else {
+			// In production: JSON to both stdout and additional writer
+			output = io.MultiWriter(os.Stdout, additionalWriter)
+		}
+	} else {
+		if debug {
+			output = zerolog.ConsoleWriter{
+				Out:        os.Stdout,
+				TimeFormat: "15:04:05",
+			}
+		} else {
+			output = os.Stdout
+		}
+	}
+
 	log.Logger = zerolog.New(output).With().Timestamp().Caller().Logger()
 }